How do I learn to accept my dad choosing his new wife over his 4 kids?

When I was 5, my parents divorced. Myself, and my siblings would go over every other weekend. My dad had a girlfriend whom he recently a couple of years ago married. I didn't really think she was a bad person...at first. She began picking off my siblings one by one. First it was my older brother. He stopped going to see my dad. Then my sister. She stopped going to see my dad. Then it was only my twin brother and I going over to visit every other weekend until we got to be old enough where we could just go over whenever we wanted. My twin then stopped seeing my dad and now I no longer talk to my dad. It kills me every day. My heart is seriously broken. I feel that his wife has come between him and his kids and it's almost like he never had any kids. I just recently had a son 3 years ago and his wife made a big deal right when my son was born that i didn't have her picture with my son on myspace. Big deal!!! Her picture was in my house. I would think that a real pic in my house versus a pic on the internet would mean more. Nope. She made a big deal about it and made my dad get really angry with me. She couldn't just come talk to me about it. She put my dad in the middle and involved him and I have really negative energy towards her for that. So right when my son was born I had to deal with this ridiculousness and heal from a c section AND learn to become a first time mom. Did I really need this at that time?! All I wanted was my dad to be a grandfather to my son and now 3 years have gone by and my son does not even know my dad. i have one picture of them from the hospital and that's it. It saddens me everyday when I think about it. Holidays go by and nothing...i use to send cards but I'm done. i thought that would help me get over it but it hasn't. Well my dads wife's son pes away last year and I sent a sympathy card not only saying how sorry I was for her loss but also that I was sorry she felt hurt by my words. I will never say sorry for the Myspace thing because that was my page. I can put whatever I want on that page. I have since deleted my myspace account because of all of this. But even after sending that card I haven't heard from my dad or stepmom. I would tolerate my stepmom if my dad wanted to come back into my life but I would keep her at arms length because i don't trust her. I just don't know what to do anymore. My dad sends my son savings bonds for christmas and just recently sent me a birthday text. That's not being a grandfather to my son or a father to me. I don't need his money...i don't need his text messages. I need my dad back. The argument was never between him and I.